System and method for selective enhancement of speech signals

Abstract

A system and method for selectively enhancing an audio signal to make sounds, particularly speech sounds, more distinguishable. The system and method are designed to divide an input auditory signal into a plurality of spectral channels having associated unenhanced signals and perform enhancement processing on a first subset of the spectral channels and not perform enhancement processing on a second subset of the spectral channels. The enhancement processing is performed by determining an output gain for at least the first subset of spectral channels based on a time-varying history of energy of the unenhanced signals associated with each channel in the first subset of the spectral channels and applying the output gain for each of the first subset of the spectral channels to the unenhanced signals to form enhanced signals associated with each of the first subset of the spectral channels. The system and method are then designed to combine the plurality of enhanced signals associated with each of the first subset of the spectral channels and the unenhanced signals associated with each of the second subset of the spectral channels to form a selectively enhanced output auditory signal.

What is claimed is: 
     
       1. A hearing aid system configured to be coupled with an ear of an individual to selectively enhance an acoustic signal to be received by the ear of the individual, comprising:
 a microphone configured to receive the acoustic signal and generate an analog electrical signal responsive thereto; 
 an analog-to-digital converter configured to receive the analog electrical signal and convert the analog electrical signal into a digital input signal; 
 a signal processor configured to receive the digital input signal and programmed to:
 divide the digital input signal into a plurality of spectral channels having associated unenhanced signals; 
 identify a first subset of the spectral channels having associated unenhanced signals corresponding to a pathological response range of the ear of the individual; 
 identify a second subset of the spectral channels having associated unenhanced signals outside the pathological response range of the ear of the individual; 
 perform enhancement processing on the first subset of the spectral channels and not perform enhancement processing on any of the second subset of the spectral channels; and 
 combine the plurality of enhanced signals associated with each of the first subset of the spectral channels and the unenhanced signals associated with each of the second subset of the spectral channels to form a selectively enhanced output signal; and 
 
 an output device configured to receive the selectively enhanced output signal and communicate the selectively enhanced output signal to the individual. 
 
     
     
       2. The system of  claim 1  wherein the pathological response range corresponds to an audio frequency range within which the ear of the individual has a pathological response. 
     
     
       3. The system of  claim 1  wherein the output device includes a speaker. 
     
     
       4. The system of  claim 1  wherein the output device includes a cochlear implant. 
     
     
       5. The system of  claim 1  wherein the signal processor is configured to use a channel selection criteria designated by a matrix corresponding to the plurality of spectral channels to perform enhancement processing on a first subset of the spectral channels and not perform enhancement processing on a second subset of the spectral channels. 
     
     
       6. The system of  claim 5  wherein the matrix includes a block Toeplitz submatrix configured to make the second subset of the spectral channels instantiated by an identity submatrix. 
     
     
       7. The system of  claim 1  wherein the signal processor, to perform enhancement processing, is further programmed to:
 determine an output gain for at least the first subset of spectral channels based on a time-varying history of energy of the unenhanced signals associated with each channel in the first subset of the spectral channels; and 
 apply the output gain for each of the first subset of the spectral channels to the unenhanced signals associated with the respective channel in the first subset of the spectral channels to form enhanced signals associated with each of the first subset of the spectral channels. 
 
     
     
       8. A method for selectively enhancing an auditory signal, comprising the steps of:
 (a) dividing an input auditory signal into a plurality of spectral channels having associated unenhanced signals; 
 (b) performing enhancement processing on a first subset of the spectral channels and not performing enhancement processing on any of a second subset of the spectral channels, wherein the enhancement processing includes:
 (i) determining an output gain for at least the first subset of spectral channels based on a time-varying history of energy of the unenhanced signals associated with each channel in the first subset of the spectral channels; and 
 (ii) applying the output gain for each of the first subset of the spectral channels to the unenhanced signals associated with the respective channel in the first subset of the spectral channels to form enhanced signals associated with each of the first subset of the spectral channels; and 
 
 (c) combining the plurality of enhanced signals associated with each of the first subset of the spectral channels and the unenhanced signals associated with each of the second subset of the spectral channels to form a selectively enhanced output auditory signal. 
 
     
     
       9. The method of  claim 8  wherein step (b) includes applying a channel selection criteria designated by a matrix corresponding to the plurality of spectral channels. 
     
     
       10. The method of  claim 9  wherein the matrix includes a block Toeplitz submatrix configured to make the second subset of the spectral channels instantiated by an identity submatrix. 
     
     
       11. The method of  claim 8  wherein a magnitude of the output gain for each of the first subset of spectral channels is inversely related to the history of energy of the unenhanced signals associated with each channel in the first subset of the spectral channels. 
     
     
       12. The method of  claim 8  wherein the step (a) includes the step of applying the input auditory signal to a plurality of polyphase multirate filters. 
     
     
       13. The method of  claim 8  wherein the step (b)(i) includes the steps of determining a weighted energy history for each channel based on the time varying history of the energy in the channel, converting the weighted energy history into an RMS history weighting value, and determining the output gain for the channel using the RMS history weighting value. 
     
     
       14. The method of  claim 13  wherein the step of determining the weighted energy history for each channel includes weighting more recent energy in the channel more heavily than less recent energy in the channel. 
     
     
       15. A system for selectively enhancing an acoustic signal, comprising:
 a microphone configured to receive an acoustic signal and generate an analog electrical signal responsive thereto; 
 an analog-to-digital converter configured to receive the analog electrical signal and convert the analog electrical signal into a digital input signal; 
 a signal processor configured to receive the digital input signal and programmed to:
 divide the digital input signal into a plurality of spectral channels having associated unenhanced signals; 
 perform enhancement processing on a first subset of the spectral channels and not perform enhancement processing on a second subset of the spectral channels, the spectral channels in the first subset of the spectral channels and the spectral channels in the second subset of the spectral channels being mutually exclusive; and 
 combine the plurality of enhanced signals associated with each of the first subset of the spectral channels and the unenhanced signals associated with each of the second subset of the spectral channels to form a selectively enhanced output signal; and 
 
 an output device configured to receive the selectively enhanced output signal and communicate the selectively enhanced output signal. 
 
     
     
       16. The system of  claim 15  wherein the output device includes a speaker configured to communicate the selectively enhanced output signal as an acoustic signal. 
     
     
       17. The system of  claim 15  wherein the output device includes a digital-to-analog converter configured to convert the selectively enhanced output signal to an analog electrical output signal. 
     
     
       18. The system of  claim 15  wherein the microphone, analog-to-digital converter, and signal processor system are contained in a hearing aid. 
     
     
       19. The system of  claim 15  wherein the output device includes a speech recognition system including a display configured to communicate text corresponding to the selectively enhanced output signal. 
     
     
       20. The system of  claim 15  wherein the signal processor, to perform enhancement processing, is further programmed to:
 determine an output gain for at least the first subset of spectral channels based on a time-varying history of energy of the unenhanced signals associated with each channel in the first subset of the spectral channels; and 
 apply the output gain for each of the first subset of the spectral channels to the unenhanced signals associated with the respective channel in the first subset of the spectral channels to form enhanced signals associated with each of the first subset of the spectral channels.